1. Field of the Invention
The present invention relates to golf balls. More particularly, the present invention relates to improvement of dimples of a golf ball.
2. Description of the Related Art
Golf balls have numerous dimples on the surface thereof. The dimples disrupt the air flow around the golf ball during the flight, thereby causing turbulent flow separation. By causing the turbulent flow separation, a separating point of air from the golf ball shifts backwards leading to the reduction of drag. The turbulent flow separation promotes the differentia between the separating points at the upper and lower sides of the golf ball, which results from the backspin, thereby enhancing the lift force that acts upon the golf ball. Such a role of the dimple is referred to as a “dimple effect”. Excellent dimples disturb the air flow more efficiently.
A variety of proposals with respect to the dimple shape have been made in an attempt to improve the flight performance. U.S. Pat. No. 5,338,039 discloses a dimple having double slopes. U.S. Pat. No. 5,536,013 discloses a dimple having a projection at the center. U.S. Pat. No. 5,735,757 discloses a dimple having a double radius shape. JP-A No. 2002-336337 discloses a dimple having a sub-dimple formed inside thereof.
Top concern to golf players for golf balls is the travel distance. In light of elevation of the travel distance, there remains room for improvement of the dimple. An object of the present invention is to provide a golf ball that is excellent in the flight performance.